<template>
    <div id="calendar">
        <!-- 年份 月份 -->
        <div class="month">
            <ul>
                <li class="arrow" @click="pickPre(currentYear,currentMonth)">❮</li>
                <li class="year-month" @click="pickYear(currentYear,currentMonth)">
                    <span class="choose-year">{{ currentYear }}</span>
                    <span class="choose-month">{{ currentMonth }}月</span>
                </li>
                <li class="arrow" @click="pickNext(currentYear,currentMonth)">❯</li>
            </ul>
        </div>
        <!-- 星期 -->
        <ul class="weekdays">
            <li>一</li>
            <li>二</li>
            <li>三</li>
            <li>四</li>
            <li>五</li>
            <li style="color:red">六</li>
            <li style="color:red">日</li>
        </ul>
        <!-- 日期 -->
        <ul class="days">
            <li @click="pick(day)" v-for="day in days">
                <!--本月-->
                <span v-if="day.getMonth()+1 != currentMonth" class="other-month">{{ day.getDate() }}</span>
                <span v-else>
                    <!--今天-->
                    <span v-if="day.getFullYear() == new Date().getFullYear() && day.getMonth() == new Date().getMonth() && day.getDate() == new Date().getDate()" class="active">{{ day.getDate() }}</span>
                    <span v-else>{{ day.getDate() }}</span>
                </span>
            </li>
        </ul>
    </div>
</template>

<script>
export default {
    data() {
        return {
            currentDay: 1,
            currentMonth: 1,
            currentYear: 1970,
            currentWeek: 1,
            days: []
        }
    },
    created: function () {
        this.initData(null);
    },
    methods: {
        initData: function (cur) {
            var date;
            if (cur) {
                date = new Date(cur);
            } else {
                date = new Date();
            }
            this.currentDay = date.getDate();
            this.currentYear = date.getFullYear();
            this.currentMonth = date.getMonth() + 1;
            this.currentWeek = date.getDay(); // 1...6,0
            if (this.currentWeek == 0) {
                this.currentWeek = 7;
            }
            var str = this.formatDate(this.currentYear, this.currentMonth, this.currentDay);
            console.log("today:" + str + "," + this.currentWeek);
            this.days.length = 0;
            // 今天是周日，放在第一行第7个位置，前面6个
            for (var i = this.currentWeek - 1; i >= 0; i--) {
                var d = new Date(str);
                d.setDate(d.getDate() - i);
                console.log("y:" + d.getDate());
                this.days.push(d);
            }
            for (var i = 1; i <= 35 - this.currentWeek; i++) {
                var d = new Date(str);
                d.setDate(d.getDate() + i);
                this.days.push(d);
            }
        },
        pick: function (date) {
            alert(this.formatDate(date.getFullYear(), date.getMonth() + 1, date.getDate()));
        },
        pickPre: function (year, month) {
            //  setDate(0); 上月最后一天
            //  setDate(-1); 上月倒数第二天
            //  setDate(dx) 参数dx为 上月最后一天的前后dx天
            var d = new Date(this.formatDate(year, month, 1));
            d.setDate(0);
            this.initData(this.formatDate(d.getFullYear(), d.getMonth() + 1, 1));
        },
        pickNext: function (year, month) {
            var d = new Date(this.formatDate(year, month, 1));
            d.setDate(35);
            this.initData(this.formatDate(d.getFullYear(), d.getMonth() + 1, 1));
        },
        pickYear: function (year, month) {
            alert(year + "," + month);
        },

        // 返回 类似 2016-01-02 格式的字符串
        formatDate: function (year, month, day) {
            var y = year;
            var m = month;
            if (m < 10) m = "0" + m;
            var d = day;
            if (d < 10) d = "0" + d;
            return y + "-" + m + "-" + d
        },
    }
}   
</script>

<style scoped>
* {
    box-sizing: border-box;
}

ul {
    list-style-type: none;
}

body {
    font-family: Verdana, sans-serif;
    background: #E8F0F3;
}

#calendar {
    width: 80%;
    margin: 0 auto;
    box-shadow: 0 2px 2px 0 rgba(0, 0, 0, 0.14), 0 3px 1px -2px rgba(0, 0, 0, 0.1), 0 1px 5px 0 rgba(0, 0, 0, 0.12);
}

.month {
    width: 100%;
    background: #00B8EC;
}

.month ul {
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: space-between;
}

.year-month {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: space-around;
}

.year-month:hover {
    background: rgba(150, 2, 12, 0.1);
}

.choose-year {
    padding-left: 20px;
    padding-right: 20px;
}

.choose-month {
    text-align: center;
    font-size: 1.5rem;
}

.arrow {
    padding: 30px;
}

.arrow:hover {
    background: rgba(100, 2, 12, 0.1);
}

.month ul li {
    color: white;
    font-size: 20px;
    text-transform: uppercase;
    letter-spacing: 3px;
}

.weekdays {
    margin: 0;
    padding: 10px 0;
    background-color: #00B8EC;
    display: flex;
    flex-wrap: wrap;
    color: #FFFFFF;
    justify-content: space-around;
}

.weekdays li {
    display: inline-block;
    width: 13.6%;
    text-align: center;
}

.days {
    padding: 0;
    background: #FFFFFF;
    margin: 0;
    display: flex;
    flex-wrap: wrap;
    justify-content: space-around;
}

.days li {
    list-style-type: none;
    display: inline-block;
    width: 14.2%;
    text-align: center;
    padding-bottom: 15px;
    padding-top: 15px;
    font-size: 1rem;
    color: #000;
}

.days li .active {
    padding: 6px 10px;
    border-radius: 50%;
    background: #00B8EC;
    color: #fff;
}

.days li .other-month {
    padding: 5px;
    color: gainsboro;
}

.days li:hover {
    background: #e1e1e1;
}
</style>
